The present invention relates to a plurality of different wireless communication systems and a mobile terminal therefor capable of switching communication systems.
Conventional wireless communication systems, which control the data delivery route, i.e., routing, for moving users are disclosed in JP-A No. 2000-183974 and No. 2000-183975. These systems are designed to group several base stations into one domain and control routing by using the technique of mobile IP for access between different domains. These systems can perform the routing efficiently within a domain and between the domains. However, the base stations are part of a single communication system, and existing techniques do not address the case of data delivery routing among different communication systems.
Currently available digital cellular systems provide data communication as well as voice communication. To better meet the demands of data communication, higher rate transmission is under study.
The trend of wireless high-speed data communication is for each communication cell to handle higher bandwidth data transmissions using a proportionately wider radio frequency bandwidth for transmission at higher data rates, and the inevitable use of higher radio carrier frequencies results in a shorter radio signal range. Consequently, the cell size becomes smaller. These high-speed data communication systems will coexist with existing wireless communication systems. Specifically, there will coexist communication systems that are high in speed but short range in service area and allocated in a spot-wise fashion. Other communication systems which are low in speed but wider in range are allocated in overlapping, wide-area coverage fashion.